A two-scale damage model for high cycle fatigue delamination in laminated composites (original) (raw)
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Fatigue damage modelling of composite materials
Composite Structures, 2002
This paper develops a mathematical model for fatigue damage evolution in composite materials. The characteristics of damage growth in composite materials are studied and compared with those of damage growth in homogeneous materials. Continuum damage mechanics concepts are used to evaluate the degradation of composite materials under cyclic loading. A new damage accumulation model is proposed to capture the unique characteristics of composite materials. The proposed model is found to be more accurate than existing models, both in modelling the rapid damage growth early in life and near the end of fatigue life. The parameters for the proposed model are obtained with experimental data. A numerical example is implemented to illustrate that the proposed model is able to accurately fit several different sets of experimental data.
Simulation of Fatigue Delamination Growth in Composites with Different Mode Mixtures
Journal of Composite Materials, 2007
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights An efficient method for modelling delamination under fatigue is proposed. The method is based on contact interaction of two layers modeled by shell elements. A method of the durability prediction using cohesive contact elements is developed. The algorithm gives an instrument for solving high-cycle fatigue problems. A coarse mesh is sufficient to obtain acceptable accuracy of results.
High Cycle Fatigue Damage Model for Delamination Crack Growth in CF/Epoxy Composite Laminates
International Journal of Damage Mechanics, 2010
This article presents the development of a fatigue damage model which helps to carry out simulation of the evolution of delamination in the laminated composite structures under cyclic loadings. A classical interface damage evolution law, which is commonly used to predict the static debonding process, is modified further to incorporate fatigue delamination effects due to high cycle loadings. An improved formulation is also presented to incorporate the ‘R’ ratio effects. The proposed fatigue damage model is identified using fracture mechanics tests like double cantilever beam, end-notched-flexure and mixed-mode bending. Then a non-monotonic behavior is used to predict the fatigue damage parameters able to carry out delamination simulations for different mode mixtures. Linear Paris plot behaviors of the above-mentioned fracture mechanics tests are successfully compared with available experimental data on HTA/6376C and AS4/PEEK unidirectional materials.
Progressive failure mechanism of laminated composites under fatigue loading
Journal of Composite Materials, 2020
A cohesive zone model for delamination propagation in laminated composites under static and fatigue loading has been derived and validated with experimental data under different mode conditions. This study presents a new approach to quantify fatigue delamination degradation based on damage mechanics to evaluate the rate of fatigue damage ([Formula: see text]). The static damage evaluation and fatigue damage degradation are derived from damage surface concept. Both static and fatigue damage linked each other to establish fatigue crack growth formula in the laminated composites. A user-defined subroutine, UMAT, has been employed to develop and implement a damage model in ABAQUS. Two different specimens; a double cantilever beam and a single lap joint were used to investigate the effectiveness of the new method. The simulation results revealed that the developed model had good agreement with experimental data available in literature.
A continuum damage model for delaminations in laminated composites
Journal of the Mechanics and Physics of Solids, 2003
Delamination, a typical mode of interfacial damage in laminated composites, has been considered in the context of continuum damage mechanics in this paper. Interfaces where delaminations could occur are introduced between the constituent layers. A simple but appropriate continuum damage representation is proposed. A single scalar damage parameter is employed and the degradation of the interface sti ness is established. Use has been made of the concept of a damage surface to derive the damage evolution law. The damage surface is constructed so that it combines the conventional stress-based and fracture-mechanics-based failure criteria which take account of mode interaction in mixed-mode delamination problems. The damage surface shrinks as damage develops and leads to a softening interfacial constitutive law. By adjusting the shrinkage rate of the damage surface, various interfacial constitutive laws found in the literature can be reproduced. An incremental interfacial constitutive law is also derived for use in damage analysis of laminated composites, which is a non-linear problem in nature. Numerical predictions for problems involving a DCB specimen under pure mode I delamination and mixed-mode delamination in a split beam are in good agreement with available experimental data or analytical solutions. The model has also been applied to the prediction of the failure strength of overlap ply-blocking specimens. The results have been compared with available experimental and alternative theoretical ones and discussed fully.
I n this research, a new model is established based on progressive fatigue damage and critical element models to simulate fatigue behaviour and predict the fatigue life of composite laminates with stress concentration. This model, called the "regional elements" model, has three major parts: stress analysis, failure analysis, and material property degradation. A critical region of the analyzed composite laminate is considered and the elements of this region are divided into critical and sub-critical layers. Using 2dimensional stress analysis, failure modes of these regional elements are investigated and material properties in the critical and sub-critical layers are changed according to sudden and gradual material property degradation rules. Gradual material property degradation is performed on the longitudinal tensile strength of critical layers and the longitudinal tensile stiffness of sub-critical layers. By the iteration of the aforementioned loop, fatigue damage modelling is completed and an estimate of the fatigue life of a composite laminate is obtained. The finite element method is used to assess the capabilities of the current model through a user-friendly computer programme. The model predicts initial and final failure loads to within 20% of experimental results for the case of static failure analysis. However, 3-dimensional stress and failure analyses are required to improve the model for fatigue failure analysis for all the configurations.
Numerical simulation of fatigue-driven delamination using interface elements
International Journal for Numerical Methods in Engineering, 2005
This paper presents a computational technique for the prediction of fatigue-driven delamination growth in composite materials. The interface element, which has been extensively applied to predict delamination growth due to static loading, has been modified to incorporate the effects of cyclic loading. Using a damage mechanics formulation, the constitutive law for the interface element has been extended by incorporating a modified version of a continuum fatigue damage model. The paper presents details of the fatigue degradation strategy and examples of the predicted fatigue delamination growth in mode I, mode II and mixed mode I/II are presented to demonstrate that the numerical model mimics the Paris law behaviour usually observed in experimental testing. Copyright © 2005 John Wiley & Sons, Ltd.
Cumulative Fatigue Damage of Composite Laminates: Engineering Rule and Life Prediction Aspect
Materials
The analysis of cumulative fatigue damage is an important factor in predicting the life of composite elements and structures that are exposed to field load histories. A method for predicting the fatigue life of composite laminates under varying loads is suggested in this paper. A new theory of cumulative fatigue damage is introduced grounded on the Continuum Damage Mechanics approach that links the damage rate to cyclic loading through the damage function. A new damage function is examined with respect to hyperbolic isodamage curves and remaining life characteristics. The nonlinear damage accumulation rule that is presented in this study utilizes only one material property and overcomes the limitations of other rules while maintaining implementation simplicity. The benefits of the proposed model and its correlation with other relevant techniques are demonstrated, and a broad range of independent fatigue data from the literature is used for comparison to investigate its performance a...
The simulation of the fatigue damage of laminated composites under multi-axial and variable amplitude loadings has to deal with several new challenges and several methods of damage modelling. In this paper we present how to account for the complex loading by using the damage hysteresis operator approach for fatigue. It is applied to a fatigue model for intra-laminar damage based on stiffness degradation laws from van Paepegem [1]and has been extended to deal with unidirectional carbon fibres. The parameter identification method is presented here and parameter sensitivities are discussed. The initial static damage of the material is accounted for by using the Ladevèze damage model and the permanent shear strain accumulation based on Van Paepegem's formulation. This approach has been implemented into commercial software. The intra-laminar fatigue damage model combines efficient methods with a low number of tests to identify the parameters of the stiffness degradation law, this overall procedure for fatigue life prediction is demonstrated to be cost efficient at industrial level.
Composites science and technology, 1992
A fatigue model has been developed for damage growth at a notch tip in carbon fibre/epoxy laminates. The damage is modelled as a series of interacting matrix cracks in various forms: splitting, delamination and transverse ply cracking. The extent of fatigue damage can be successfully predicted for a family of (901/0j),s and (90/+ 45/0)s laminates. In this second paper of four, a damage-based model is proposed which can explain the effect of cyclic tensile loading on the post-fatigue strength and stiffness of a notched laminate.